Mussel-inspired modification of Si-PDA-BNNS-OH@PDA-CNF composite films with excellent thermal conductivity and mechanical properties

Cellulose nanofibers (CNF) feature a three-dimensional nanofiber network, excellent mechanical properties, and abundant surface hydroxyl groups, facilitating the integration of boron nitride (BN) for fabricating flexible composite films with high thermal conductivity. However, achieving a balance between high thermal conductivity and strong mechanical strength at high BN loadings remains a formidable challenge. A mussel-inspired strategy is employed, in which BNNS-OH and CNF are coated with polydopamine (PDA) to improve their interfacial adhesion and compatibility. The PDA-BNNS-OH is then silanized with 3-aminopropyltriethoxysilane to acquire a positive charge, enabling its subsequent electrostatic adsorption onto PDA-CNF and assembly into a robust film. At a high filler loading of 60 wt%, the resultant composite film achieves an outstanding in-plane thermal conductivity of 18.9 W m −1  K −1 , a 1250% improvement relative to the pure CNF film. Remarkably, this marked enhancement is achieved without compromising the film's high electrical insulation capability, as evidenced by a volume resistivity exceeding 10 11  Ω m, while still delivering a substantial tensile strength of 49.5 MPa. These synergistic enhancements are attributed to the optimized interfacial bonding, which effectively reduces thermal resistance and suppresses phonon scattering. This interface design strategy offers a promising pathway for developing advanced thermal management materials.